"Check engine" light kicking in at 4-5k rpm

[Jezza_hr]

On the way to Japfest today my car seemed to show an interesting problem. The 'check engine' light kicked in on the motorway at 5k rpm (if I drop down below 4 it dissapears) Looking to the oil pressure and water temp read outs, the water temp is normal and the oil pressure sits a tad higher than normal.

Once we got to Japfest we were a bit stumped as to what it could be. I checked the radiator and it's boiling hot at the top and cold at the bottom. I squeezed the rad pipes and they had very little pressure in them, so my initial guess is that it's a faulty thermostat or water pump.

However, what I dont understand is, why is only the oil pressure going above normal and not the water temp? the water temp sensor seems to show normal readouts like I say. Could it be that the water in the engine is just enough to show a cool readout yet the engine oil is getting hot enough to show a pressure hike? im a bit confused

[Jezza_hr]

Right, the diagnostics are giving me an error 6, which means there is no ground heading back to the ECU, which explains my flaming exhaust as the ECU must be compensating with extra fuel since its not getting a reading from the dizzy. That in turn could explain why my engine is getting high in oil pressure as it's running quite rich?

Checking on the dizzy it appears to be a tad melted from lack of a heat shield next to the manifold., yet I can't see where the ground is that heads back to the ECU, can anyone point me in the right direction?

[projectrollas]

i had the similar problem w/my coupe. here in the states there is a temp sensor for the ecu in front of the engine near the temp sensor for the gauge. that was loosening it self w/the vibration of the rpms. it would run rich and would also puff out a small flame at high shift points. hope it helps.

[Jezza_hr]

Thanks, I will check it out.

[irishtwincam]

Jezza_hr Wrote:Right, the diagnostics are giving me an error 6, which means there is no ground heading back to the ECU,...

For an AE86 error code 6 is:

6 RPM signal. No Ne, G signal (engine revolution sensor) signal to ECU within several seconds after engine is cranked. No Ne, G signal (engine revolution sensor) signal to ECU within several seconds after engine reaches 1,000rpm. Distributor circuit.
Distributor.
Starter signal circuit.
ECU.


This would stop your car from starting or running.
ECU thinks if the engine isnt spinning over, dont send fuel or spark.

[Jezza_hr]

That's a bit odd as it is actually running It did give me fault number 9 aswell, but I knew about that one already.

EDIT: Aha, I think I know the problem there. It's to do with when my engine wouldn't start a while back due to a cabling issue and has since been sorted. Although the ECU hasnt been reset. So it must be something else